The present invention generally relates to a copying machine and more particularly, to an optical system and a simplified continuous copying operation of a copying machine having an original platform on which an original is placed and an original cylinder around which an original is wound.
Conventionally, when a large number of copied paper sheets are to be produced from one original through operation of a copying machine, it has been a common practice that an original which is placed in position on an original platform has been copied through required times of reciprocating scanning of an optical system or the original platform. In this method, however, since the reciprocating motion of the optical system or the original platform is required for each paper sheet on which the original is copied, the copying machine has been not only relatively slow in copy speed, but also large in vibration, noise or the like.
Meanwhile, there has been commercialized a copying machine having an original cylinder around which the original is wound, wherein the original is copied through the scanning by the rotation of the original cylinder in order to solve the aforementioned drawbacks. In case where a continuous copying operation is carried out on a sheet-like original by the above described copying machine, the optical system is set so that a stationary exposure position is applied with light therefrom and reflected light at the exposure position is transmitted to a photosensitive body, while the original cylinder rotates at the exposure position synchronously with the rotation of the photosensitive body.
In such a copying machine, it is necessary to provide two sets of optical systems such as an optical device for copying the original placed on the original platform and another optical device for copying the original wound around the original cylinder. However, it is not desirable for the copying machine to be provided with two sets of optical devices each having an exposing lamp, one or more reflecting mirrors, a copying lens or the like, since the copying machine tends to be large both in size and weight, high in cost and the like.
Furthermore, in the case where a thick paper, a book or the like is used as the original, since it can not be directly set on the original cylinder for the continuous copying operation, it can not be consecutively copied unless it is once copied on the original platform for the subsequent continuous copying operation wherein a copied paper sheet is set on the original cylinder as the original. Even if the original is not a thick paper sheet, since it is possible that the original may be damaged by the rotation thereof together with the original cylinder, the original has necessarily been first copied on the original platform for the subsequent continuous copying operation wherein the copied paper sheet is wound around the original cylinder as the original, in case of an important original, as well as in case of the thick original described above.